Implement periodic sync to agents

[horazont]

We’re seeing in our clusters that the periodic safeguard sync isn’t working all the time. Syncs required due to changed configuration are executed properly though.

[horazont]

The reason is that no periodic sync is even implemented, hah.

In fact we only sync on changes which could affect our config, which is often enough in a busy cluster (endpoints and node objects updating). In a more idle cluster, you don’t see such changes very often.

Of course, a periodic sync is desirable for ensuring consistency even if agents lose connectivity for a while or are restarted or added or whatever, so it should be added. Let us fight the eternal fight against entropy